What Process Divides the Cytosol, Organelles and Proteins?
The process that divides the cytosol, organelles, and proteins between two new cells is cytokinesis — the final stage of cell division that physically separates one cell into two daughter cells after the nucleus has already divided. During cytokinesis, the cytoplasm (the cytosol plus everything suspended in it, including organelles and soluble proteins) is split so each daughter cell receives its own functional set of cellular components. In animal cells this happens through a contractile ring that pinches the cell in two; in plant cells it happens through a new cell plate that builds a wall down the middle.
If you have ever asked what process divides the cytosol organelles and proteins, the short answer is cytokinesis. Mitosis divides the chromosomes; cytokinesis divides almost everything else.
Cytokinesis: The Dividing Process
Cytokinesis is the stage of the cell cycle in which the single parent cell is split into two separate daughter cells. It follows mitosis, the phase that separates duplicated chromosomes into two identical nuclei. By the time cytokinesis begins, each end of the cell already has a complete set of genetic instructions — but those instructions are useless without the cytoplasm needed to run a cell.
That is where cytokinesis comes in. It partitions the cytosol, the fluid portion of the cytoplasm, along with the organelles, proteins, and other molecules suspended in it. According to the National Center for Biotechnology Information, cytokinesis typically starts in late anaphase or early telophase and finishes shortly after the nuclear envelope reforms.
The process is highly coordinated. Molecular signals from the mitotic spindle tell the cell cortex — the layer of cytoskeleton just inside the membrane — where and when to begin pinching. Without that signal, division stalls, and a single cell can end up with two nuclei instead of becoming two cells.
How Cytosol and Organelles Divide
During cytokinesis, the cytosol and its contents are not copied the way DNA is. They are physically split. The dividing apparatus constricts around the cell’s equator, and whatever lies on one side of that constriction ends up in one daughter cell, while everything on the other side goes to the other.
Organelles are handled in different ways depending on the type:
- Membrane-bound organelles such as mitochondria, the endoplasmic reticulum, and the Golgi apparatus are distributed between the two halves as the cytoplasm is divided. Cells that need more of a given organelle will often duplicate it before division so both daughters get enough.
- Small organelles and vesicles simply diffuse or are carried along with the flowing cytosol.
- Soluble proteins are dissolved in the cytosol, so they are split passively along with the fluid — each daughter gets roughly half, though the split is rarely perfectly even.
A quick worked example
If a cell in G2 phase contains 200 mitochondria, it typically duplicates them so that about 400 exist before division. After cytokinesis, each daughter cell inherits approximately 200. The same logic applies to the Golgi stacks and endoplasmic reticulum, which fragment during mitosis and reassemble in each daughter cell. You can see this partitioning explained step by step in resources from Khan Academy, which walks through how the phases of mitosis and cytokinesis connect.
Animal vs. Plant Cell Division
The mechanics of cytokinesis look very different in animal and plant cells, mostly because plant cells have a rigid cell wall that cannot be pinched inward.
| Feature | Animal cells | Plant cells |
|---|---|---|
| Division structure | Contractile ring of actin and myosin | Cell plate made of vesicles |
| Direction of growth | Furrow pinches inward from the edges | Plate grows outward from the center |
| Final result | Cleavage furrow splits the cell in two | New cell wall divides the cell |
| Organelle handling | Split by the furrow as it closes | Trapped on either side of the growing plate |
Animal cells: the cleavage furrow
In animal cells, a ring of actin and myosin filaments forms just beneath the plasma membrane at the cell’s equator during late anaphase. This contractile ring tightens like a drawstring, creating a groove called the cleavage furrow. As the ring constricts, the furrow deepens until the cell is pinched into two daughters. The Nature Scitable library describes this contractile ring as the core engine of animal cytokinesis, and it is powered by the same actin-myosin interaction that shortens muscle fibers.
Plant cells: the cell plate
Plant cells cannot pinch because the cell wall is too stiff. Instead, vesicles carrying cell wall materials gather along the equator and fuse into a flat disc called the cell plate. The plate grows outward until it meets the existing cell wall, then matures into a new wall separating the two daughters. Each side keeps the organelles that happened to be there when the wall sealed. This is also why plant cells maintain their rectangular shape after division while animal cells round up briefly during the pinch.
Why Equal Distribution Matters
Accurate division of cytosol, organelles, and proteins is not a housekeeping detail — it determines whether daughter cells can survive and function.
If the split is uneven, consequences follow:
- Metabolic failure. A cell that receives too few mitochondria cannot produce enough ATP through oxidative phosphorylation to meet its energy needs.
- Growth problems. Daughter cells that lack enough ribosomes and soluble proteins cannot synthesize new materials quickly, slowing growth and division.
- Genetic stability. Errors in the division machinery can cause cells to fuse back together or produce extra nuclei, a condition called multinucleation that is linked to abnormal cell behavior.
Cytokinesis is also tightly regulated in healthy tissue so that cell numbers stay balanced. When the process is disrupted, cells may divide without properly partitioning their contents, which is one reason researchers study cytokinesis in the context of developmental disorders and cancer biology. This is general, textbook-level information; for any personal medical question about cell division, growth, or disease, consult a qualified healthcare professional.
Key Takeaways
- Cytokinesis is the process that divides the cytosol, organelles, and proteins between two daughter cells after mitosis.
- In animal cells, an actin-myosin contractile ring forms a cleavage furrow that pinches the cell in two.
- In plant cells, a cell plate grows outward from the center and matures into a new cell wall.
- Organelles and soluble proteins are partitioned passively with the cytosol rather than copied like DNA.
- Unequal or faulty distribution can impair metabolism, slow growth, and destabilize normal cell function.
